TRANSPORT OF CAROTENOIDS AND FAT-SOLUBLE VITAMINS 335 



and Herraiz, 564 who observed a fluorescence of vitamin A in portal blood 

 similar to that noted by them in lymph. One must conclude that the 

 evidence is overwhelming that vitamin A is not transported in appreciable 

 amounts from the intestine by way of the portal route. Table 10 records 

 some especially convincing experiments which have been cited as proof of 

 the above statement. 



According to Eden and Sellers 565 and Bean el al., b67 most of the absorp- 

 tion of vitamin A occurs in the upper part of the intestine. 



(8) The Transport of the Vitamins D in the Lymph and Blood 



The pathway for transportation of the vitamins D from the intestine 

 to the tissues is not known. There is no reason to suppose that these 

 vitamins do not follow the same pathway as has been reported for fats, 

 carotenoids, vitamins A and K. This would involve the lymphatic 

 system as the principal if not the exclusive route for the transfer of the 

 vitamins D from the epithelial cells of the intestine to the blood stream, 

 after which its further distribution would be mediated through the blood 

 stream. In keeping with this concept, the portal route would be of little 

 or no importance in bringing about the removal of vitamin D from the 

 intestine. 



The presence of vitamin D in the blood has been established by a num- 

 ber of investigators. Warkany 568 ' 569 reported that 100 ml. of human 

 serum contained an average of 100 LIT. (50 to 135 I.U.) while, in rabbits, 

 the mean vitamin A content was 50 I.U. per 100 ml. Hess and his col- 

 laborators 570 have reported that, in cows, the plasma contains about four 

 times the concentration of vitamin D that is present in the corpuscles. 

 Moreover, higher levels of vitamin D were found after high dosages of 

 irradiated ergosterol had been given. 571 The concentration of vitamin D 

 in whole blood was shown to vary between 40 and 67 I.U. per 100 ml., 

 depending upon the quantity of vitamin D 2 administered. 569 



(4) The Transport of the Vitamins E in the Lymph and Blood 

 There is no reason to suppose that the method of transport of the vita- 



567 W. B. Bean, M. Franklin, J. F. Embick, and K. Daum, ./. Clin. Invest., SO, 263-273 

 (1951). 



568 J. Warkany, Am. J. Diseases Children, 52, 831-847 (1936). 

 669 J. Warkany, Biochem. Z., 2B3, 415-426 (1937). 



570 A. F. Hess, R. F. Light, C. N. Frey, and J. Gross. J. Biol. Chem., 97, 369-377 

 (1932). 



571 A. F. Hess, M. Weinstock, and J. Gross, Proc. Soc. Exptl. Biol. Med., SO, 1357-1358 

 (1933). 



